Excavating tool and method for excavating rock, minerals and the like

ABSTRACT

The invention provides an apparatus for excavating rock, minerals and the like, which includes a hub  22  connected to a rotatable drive. Cutting elements such as picks  20   a  are supported by tool holders connected to the hub. The picks  20   a  project radially from the hub, and are arranged in oblique relationship to the axis of rotation of the hub. The drive means is preferably designed to impart an eccentric, superimposed percussive action on the hub  22.  During use the hub  22  is positioned facing a rock surface and urged along the rock face in transverse relationship to the axis of rotation of the hub, thereby causing the picks  20   a  to undercut an adjacent region of rock, and thereby excavating successivel layers of rock.

FIELD OF THE INVENTION

[0001] This invention relates to a method of excavating rock, minerals and the like. The invention further relates to an apparatus for excavating rock, minerals and the like.

BACKGROUND TO THE INVENTION

[0002] There are various known tools for excavating rock, minerals and the like, by ripping or by planar cutting. Such tools may include rotating disks or drums, operating in milling-fashion. The present invention makes it feasible to excavate hard rock, and extremely hard minerals in particular, efficiently and economically in relation to prior known methods. More particularly the present invention involves, among other aspects, operating a rotating cutting tool about an axis forming an angle in relation to a rock face, instead of being arranged in parallel relationship to it.

[0003] In order to maximise excavating rates while minimising tool abrasion and power consumption, a rock or mineral formation is cut in thin layers employing pick-like cutting tools operating at relatively high driving rates, and releasing fragmented rock or mineral into a clearance space adjacent to the cutting path of the tools. The cutting path may be linear path (see arrows) or arcuate. Excavating apparatus according to the invention may include individual or collective cutting heads, arranged in vertical relationship to each other, or in sequential relationship to each other in the cutting direction. The cutting heads preferably operate by superimposed percussion, particularly in very hard material, employing rapidly propelled, counterbalanced eccentric drives having slowly rotating, percussively operating tools, see for example EP 00115139.8.

DESCRIPTION OF THE DRAWINGS

[0004] The invention is described below by way of example with reference to the accompanying schematic drawings, in which

[0005]FIG. 1 shows a vertical sectional view of a first embodiment of an excavating apparatus according to the invention;

[0006]FIG. 2 shows a vertical sectional view of a second embodiment of the invention, having a dual cutting head;

[0007]FIG. 3 shows a vertical sectional view of a cutting apparatus similar to that of FIG. 1, adapted for superimposed percussive operation;

[0008]FIG. 3a shows an end view along the axis of rotation of the apparatus of FIG. 3, illustrating the orientation of the cutting chisels forming part of it;

[0009]FIG. 4 shows a vertical sectional view of a cutting apparatus according to the invention, having a pair of cutting heads arranged in sequential relationship to each other in the cutting direction;

[0010]FIG. 5 shows a vertical sectional view of a further cutting apparatus according to the invention having a pair of cutting heads arranged in vertical relationship to each other;

[0011]FIG. 6 shows a vertical sectional view of an excavating apparatus according to the invention having a cutting wheel and tool holders integrally connected to each other;

[0012]FIG. 7 shows a vertical sectional view of an excavating apparatus according to the invention, having a cutting head describing an arcuate path during use;

[0013]FIG. 8 shows a vertical sectional view of an excavating apparatus according to the present invention in which the axis of rotation of the cutting head is in oblique relationship to the rock face being excavated;

[0014]FIG. 9 shows a vertical sectional view of a further excavating apparatus according to the invention, similar to the one shown in FIG. 8, having a composite cutting head; and

[0015]FIG. 10 shows a vertical sectional view of a further excavating apparatus according to the invention, having a plurality of composite cutting heads arranged in juxtaposition to each other.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0016] The respective drawings show only some embodiments of the invention, by way of example.

[0017] The excavating apparatus shown in FIG. 1 has interchangeable milling tools (1) connected in to a rotatable disk, forming a hub that is propelled by a drive motor (2). The milling tools (1) project radially from the disk, and are arranged in oblique relationship to its axis of rotation. A layer of rock or mineral, illustrated schematically by reference numeral (3), is released by undercutting a layer of the rock or mineral during use of the apparatus. A lead-arm (2 a) is provided for continuously monitoring a predetermined depth of excavation.

[0018] In FIG. 2, reference numeral (2) indicates a drive means for rotating and activating a cutting head of an excavating apparatus having a pair of cutting tools (4) and (5) mounted on a common axis of rotation. Further cutting tools may be provided, each excavating a respective layer of rock or mineral.

[0019]FIG. 3 depicts a drive assembly for an excavating apparatus according to the invention, employing a superimposed percussive system (6). The system (6) includes a rapidly rotatable eccentric sleeve (7) connected to a drive (7 a), together with a counterweight (8), which is indirectly supported by a supplementary bearing (8 a) in the present embodiment, and a reduction gear arrangement (11) comprising an internally toothed ring gear meshing with a cog-wheel having a stub-axle (11 a) for optionally regulating the rate of rotation of a cutting tool (10). A radially oscillating drive shaft (9) for the tool (10) is propelled by the gear arrangement (11) at a reduced rate of rotation. During use the tool (10) forms an angular clearance space (12) with an adjacent portion of the rock face being worked. The specific angle of attack of each chisel forming part of the tool (10), in relation to the adjacent rock face, is illustrated in end view in FIG. 3a).

[0020]FIG. 4 illustrates a method of selectively excavating a reef of a valuable mineral having a thickness (17). A leading excavating tool (13) has a diameter in the order of 300 mm, whereas a trailing tool (18) for excavating the reef to its full thickness has a diameter in the order of 800 mm.

[0021]FIG. 5 illustrates an apparatus which, as an alternative to the single excavating tool (18) shown in FIG. 4, has excavating tools (19) with respective diameters in the order of 400 mm each, arranged vertical juxtaposition, for selective reef excavation.

[0022]FIG. 6 illustrates a preferred embodiment of the invention in which the cutting tool includes a disk (22) is integrally connected to respective tool holders. A quick-release coupling (23) provides a means for rapid interchanging the cutting tool. The cutting tool may be equipped with wedge shaped, rigidly mounted chisels (20 b), that are preferably replaceable, or with known interchangeable picks (20 a) having shanks of circular cross section held captive by retaining clips (27). The cutting tool is propelled by a principal drive shaft (24), which is optionally rotatable about its central axis (25), or in eccentric percussive mode, rotating about an offset axis (26).

[0023] The excavating apparatus illustrated in FIG. 7 corresponds substantially to that shown in FIG. 1. A drive means (28) propels a set of tools (29) arranged in oblique relationship to the adjacent rock face, forming an imaginary angle (30). The apparatus shown in FIG. 7 further includes supplementary tools (31) for initial penetration of the rock in the direction indicated by the arrow (32). When the depicted apparatus is employed for arcuate excavation the apparatus rotates about a pivot point (34) spaced from the axis of rotation of the drive means (28), thereby producing the required clearance space (12) between the rock face and the cutting tools (29).

[0024] In the embodiment shown in FIG. 8 cutting tools (29) operate in corresponding fashion to those illustrated in FIG. 7. The oblique relationship between the tools (29) and the adjacent rock face is, however, attributable to the orientation of the drive shaft (33) bearing the tools, which operate in undercutting fashion, thereby excavating the rock in successive layers.

[0025] The different types of apparatus illustrated in all of the drawings mentioned above generally operate by urging the rotating cutting tool towards an adjacent rock face, while the respective cutting elements such as picks, chisels or the like are directed in oblique relationship to the rock face itself.

[0026] It is generally feasible in all cases to reduce and in some cases to eliminate excessive axial thrust, and excessive wear on the tools during undercutting operations, by appropriate selection of the approach angle of the picks, chisels or the like shown in FIGS. 1 to 7, or by controlling the orientation of the axis of rotation of the drive shaft (33) in FIG. 8.

[0027] The apparatus illustrated in FIG. 9 generally corresponds to that of FIG. 8. The apparatus of FIG. 9 includes several cutting tools laterally spaced form each other, and offset against each other for excavating rock in successive layers. The arrow (35) indicates excavation layer-wise excavation along a straight-lined path. The arrow (36) denotes arcuate excavation along a curved path (33 a), illustrating an alternative method of excavation. The diameters of the picks (37) are preferably equal.

[0028]FIG. 10 depicts a so-called tri-header (38) excavating apparatus according to the invention, having a relatively large width, in the order of 1 m, and a diameter of 0.5 m. This apparatus preferably operates in undercutting fashion, following a path denoted by the arrow (35), preferably for preselected reef excavation, or for ripping purposes. 

1. A method of excavating rock which includes the steps of positioning a cutting tool having a rotatable hub equipped with cutting elements projecting radially from the hub, adjacent to the rock with the hub facing a clear surface of the rock; and urging the rotating hub along a path in transverse relationship to its axis of rotation, thereby causing the cutting elements to undercut adjacent portions of the rock.
 2. A method of excavating rock according to claim 1 which includes the further step of sequentially undercutting the rock by urging a further, similar rotating cutting tool having a hub with a larger diameter than that of the first, along substantially the same path as that followed by the first cutting tool.
 3. A method of excavating rock according to claim 1 which includes the further step of simultaneously undercutting the rock by means of a further, substantially identical rotating cutting tool, with both tools operating in coplanar relationship and in vertical juxtaposition to each other.
 4. A method of excavating rock according to claim 1 in which the cutting elements are directed in oblique relationship to the hub, towards the rock surface.
 5. A method according to claim 1 in which the cutting elements are directed in oblique relationship to the rock surface by setting the orientation of the axis of rotation of the hub in oblique relationship to the rock face.
 6. An apparatus for excavating rock, which includes a cutting tool having a hub connected to a rotatable drive; and cutting elements connected to the hub, and projecting radially from the hub, the cutting elements being arranged in such a fashion that in use they obliquely undercut adjacent portions of rock when the hub is urged along a clear rock surface, in transverse relationship to the axis of rotation of the hub.
 7. An apparatus for excavating rock according to claim 6 in which the rotatable drive is designed to impart a superimposed, eccentric percussive action on the hub during use.
 8. An apparatus for excavating rock according to claim 6 or claim 7, which includes a further, similar cutting tool having a hub with a larger diameter than that of the first, the hubs being interlinked and arranged in substantially co-planar relationship to each other for sequentially undercutting the rock by causing the cutting tool with the larger hub to trail the path of the smaller cutting tool during use.
 9. An apparatus according to claim 6 or claim 7 which includes a further, substantially identical cutting tool, both cutting tools being interlinked and arranged in co-planar relationship and vertical juxtaposition to each other for simultaneously undercutting adjacent portions of rock.
 10. An apparatus for excavating rock according to any one of claims 7 to 9 in which the hubs are interchangeable, and counterbalanced in relation to the drive means.
 11. An apparatus for excavating rock according to any one of claims 6 to 10 in which the hub of each cutting tool has holders forming an integral part of the hub, for holding the cutting elements.
 12. An apparatus for excavating rock according to claim 11 in which each hub is counterbalanced in relation to its associated drive means, and is interchangeable by way of a quick-release coupling. 